dirt bike fork on ebike

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frenchkiss   100 mW

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dirt bike fork on ebike

Post by frenchkiss » Feb 21 2017 5:15pm

any chance to fit this fork on vector/qulbix frame? thanks :)

https://www.minimx.fr/fr/fourche-dirt-b ... protection

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MadRhino   100 GW

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Re: dirt bike fork on ebike

Post by MadRhino » Feb 21 2017 5:54pm

Many factors to account for.

Yes if:

- you can make custom steering gear with upper and lower crowns, or custom headset adapters and use motorcycle handlebar assembly.

- you don't need adjustments and can tune a fork by the means of internal mods.

- you are willing to lace your front wheel to a motorcycle hub, or make custom axle and spacers to fit a bicycle hub.

- you are willing to use their brake, or make a custom brake adapter bracket.

- you are willing to accept the weight penalty.
Make it fool-proof, and I will make a better fool.
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Drunkskunk   100 GW

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Re: dirt bike fork on ebike

Post by Drunkskunk » Feb 21 2017 11:03pm

Also, that 730mm fork is tiny. It's a fork for a mini bike for 5 year olds. They mounting 12" wheels. You could mount it to a Vector style frame, but it's sure going to look funny.
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robo4   100 mW

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Re: dirt bike fork on ebike

Post by robo4 » Feb 21 2017 11:58pm

I have that size forks from a pit bike
does it look small ?
100_0165.JPG
100_0163.JPG
home made carbon frame with pit bike forks and swing arm, 19in rims, QS205 200mm dropout, 24 fet 80A controller, and 440 18650's
second bike UMF freddy1 with 1000w motor and 500-1000w 48v sine wave controller

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Hyena   100 GW

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Re: dirt bike fork on ebike

Post by Hyena » Feb 22 2017 12:59am

MadRhino wrote: - you can make custom steering gear with upper and lower crowns, or custom headset adapters and use motorcycle handlebar assembly.
- you don't need adjustments and can tune a fork by the means of internal mods.
- you are willing to lace your front wheel to a motorcycle hub, or make custom axle and spacers to fit a bicycle hub.
- you are willing to use their brake, or make a custom brake adapter bracket.
- you are willing to accept the weight penalty.
I reckon the weight is the main downside. Pit bike forks are like 3-5x the weight of mtb ones. I nearly died the first time I lifted a set!
The upside is all things pit bike are cheap so if you're going to use pitty forks, again at the expense of extra weight you can also use a moto front wheel and brakes and it'll all bolt straight up. Once you mess around getting the correct size bearings / steerer sorted the whole front end would be cheaper than a single set of mtb forks.
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Chalo   100 GW

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Re: dirt bike fork on ebike

Post by Chalo » Feb 22 2017 3:34am

You have to remember that these folks are burning petroleum instead of employing brain cells. These things tend to work only by throwing more and more energy at the equation to make it balance out.

I think you'd be better off using more or less any air sprung fork from more or less any bicycle application. That way, you can probably correct whatever deficiencies you encounter by changing air pressure or oil viscosity.

Disregard my comment if you're intending to nail jumps at 60mph on something that began life as a bicycle. In that case, God help you and release me from liability.
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frenchkiss   100 mW

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Re: dirt bike fork on ebike

Post by frenchkiss » Feb 22 2017 4:27pm

thanks all for replies,

nice bike robo4! :)

- 730mm its the same size of a DNM fork
- i will use this front brake with motorbike handlebar too for not did custom work
- the weight isnt a problems
- this fork and brake are used for 8-13hp motorbikes, i thinks its good quality for 5-10kw ebikes
- the axe of wheel is 15mm, we can fit a normal 26" bike downhill wheel

sorry i didnt understand this: "you can make custom steering gear with upper and lower crowns"
that means i need did some work for fit the middle crown of fork into the frame of bike?

thanks :)

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Re: dirt bike fork on ebike

Post by markz » Feb 22 2017 6:38pm

frenchkiss wrote:sorry i didnt understand this: "you can make custom steering gear with upper and lower crowns"
that means i need did some work for fit the middle crown of fork into the frame of bike?

thanks :)
Well in that link, all you got are two tubes which are suppose to replace broken tubes, and you reuse the steering tube and the crown(s) of whatever was on the pitbike fork before.

Yes you will need to do work/fabrication. You will need a welder, and be proficient at welding. Then you need to figure out the bearing races, which bearings you will be using.

It will be better to buy an entire front fork, then deal with the steering tube. Cut, and swap in a bicycle steering tube from a steel fork. Again you will need a welder and know how to weld.

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Re: dirt bike fork on ebike

Post by markz » Feb 22 2017 6:41pm

http://www.kijiji.ca/v-motorcycle-parts ... nFlag=true

Look at that, frocking heavy as shit. Why dont you buy a used bicycle fork, and do as Chalo said.

Here is a steering head image
http://www.triumphrat.net/attachments/s ... 271930.jpg

Would the head tube be compatible with bike?
Then the bearing issue.

robo4   100 mW

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Re: dirt bike fork on ebike

Post by robo4 » Feb 23 2017 4:13am

yes a lot heavier than a cycle fork
I actualy had a complete donor pit bike frame I cut the steering head out and made my own tough carbon frame around it so the fork used the original top clamps
mine ended up as 7.2 kw max and I'm happy with it being as heavy as it is (440 x 18650 inside)
wheels are both 19 moto rims

if you are committed to the weight build to handle it
if you want a light bike then build for that

if you are going to purchase items and assemble then go with a proven recipe, what do the other guys use on your frame?
it will be the easiest to use the same even if it is more expensive up front , you will save on the headaches later
there is no reason a down hill bike fork cant handle the weight , but you would probably need a quality set
if I were you I would use the D/H bike fork that's what your frame is made to suit
home made carbon frame with pit bike forks and swing arm, 19in rims, QS205 200mm dropout, 24 fet 80A controller, and 440 18650's
second bike UMF freddy1 with 1000w motor and 500-1000w 48v sine wave controller

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MadRhino   100 GW

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Re: dirt bike fork on ebike

Post by MadRhino » Feb 23 2017 8:21pm

Yep, it can be pretty simple if you are willing to use the complete motorcycle front end. Then you only need to adapt a headset to fit the motorcycle steering pin to your bike. But, now the weight penalty is huge because all the front end components together ( tire, wheel, disc, caliper, hose, lever, handlebar, stem, crowns...) are much heavier that the biggest of bicycle components. This extra weight will call for more, since you will need a bigger battery to maintain your range. After that, you will not be able to achieve the same performance because of all this weight. Your bike will be slower, it will take longer to brake and accelerate.
Make it fool-proof, and I will make a better fool.
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markz   100 GW

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Re: dirt bike fork on ebike

Post by markz » Feb 24 2017 3:10pm

If you can get the moto stuff for dirt cheap if not free, and you are going high power then I see it worthwhile.
I honestly looked at doing it weeks ago, thats why this thread peaked my interest. It fell into my theft proof, frocking ugly bicycle image, where the thief wouldn't have a clue what the unknown bicycle was, and therefor would skip it in a nanosecond, for a recognizable bicycle. The idea is still lingering, because I want a bike where I can lock it up on a bike rack at the transit train station, without needing a bicycle lockers at $12/month. Two real options available to me, use of bike locker and a cheap $200 setup (motor/controller and take the expensive battery with me), or a bike rack with quick release mid-drive motor + controller and of course take the battery with me. No one ever pays attention to the bike lockers, I have rarely seen anyone use them, but once I start using it often you never know.

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the12be   100 W

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Re: dirt bike fork on ebike

Post by the12be » Feb 27 2017 2:02pm

Yes that would work

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kneedeep   100 W

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Re: dirt bike fork on ebike

Post by kneedeep » Mar 13 2017 11:40pm

Just a random FYI. I was on kijiji and found a 21" rim I wanted the spoke nipples from, when I picked up the parts the guy had a set of forks he wanted gone. He said $5 so I grabbed them but don't need them then I remembered this thread. The forks fit the bomber crowns exact fit just 6.5" longer, the guy said they were from a RM250 I think.
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Re: dirt bike fork on ebike

Post by markz » Mar 14 2017 12:32am

Nice!

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kneedeep   100 W

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Re: dirt bike fork on ebike

Post by kneedeep » May 14 2017 12:33am

Just fallowing up on a bad idea that could be fun and will happen someday. These were the trees inertiaproject was selling direct fit onto dirt bike forks you would just want to use forks with disc brake tabs to start and then sort out the spacing.
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Chinese Ebay build in progress https://endless-sphere.com/forums/viewt ... 12&t=86149 , been through half a dozen scooter ebikes..No More of those.

I like to build it better than I can buy it. I like to think outside the box...Come to think of it where is that box?

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Re: dirt bike fork on ebike

Post by ecycler » May 17 2017 4:48pm

kneedeep wrote:Just fallowing up on a bad idea that could be fun and will happen someday. These were the trees inertiaproject was selling direct fit onto dirt bike forks you would just want to use forks with disc brake tabs to start and then sort out the spacing.
Nice! I wish I had picked up a set of those trees before he sold out.
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minde28383   1 kW

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Re: dirt bike fork on ebike

Post by minde28383 » Feb 01 2018 9:13pm

My two cents into safety.

Let us be more specific. Shall we :)


Pit bike forks are from 500mm up to almost 800mm. You can choose length the same as dh forks, 730mm or 750mm.
Prices:
pit bike DNM fork about 300eu - 400eu. 735mm weights 6.28kg to be specific.
Faceace fork is simial in price and weight.

Above two mentioned pit bike forks are not worse in quality compared with DNM8, opposite, they are better for heavy bikes due ability to install pit bike brakes.

So let us add up.

Pit bike fork weighs 6kg
triple clamp 1kg (maybe this is included in the fork weight, can't tell right now)
front wheel 4kg (if you use 17 mc pit bike wheel) / (if bicycle wheel take put 1 or 2 kg)
brakes 1kg (yes, they are not high end but work better than any pricy dh brakes)
and little unforeseen stuff like axle or smth 1kg

Pit bike:
So, pit bike front end - 13kg overall. Probably you can do 11kg or even less if you use bicycle wheel.

Bicycle:
Downhill bicycle front end (fork, tyre, rim brakes) 6kg or 7kg or even 8kg if with mc tyre.

Therefore pit tike front end is not too heavy, especially if you plan to go fast, 70km/h or so.

Bicycle brakes are not sufficient for heavy and fast ebikes. Cheap rotors have not much metal and gets hot fast, some have cooled rotors but hey are still are too thin, brake pads have a small surface, wear out quickly.

In pic you can see pit bike fork.
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minde28383   1 kW

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Re: dirt bike fork on ebike

Post by minde28383 » Feb 01 2018 9:19pm

BTW
This fork in pic is not DNM or Fastace. Maybe its Volt (Version1 - 100eu or Version2 - 200eu) or some cheap analog. Can't tell from view.
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MadRhino   100 GW

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Re: dirt bike fork on ebike

Post by MadRhino » Feb 01 2018 11:17pm

MInde

Your front end weight estimation is biased

My commuter front end, including all components: headset, complete Boxxer WC fork with DM stem, wheel with 24X3.0 tire, caliper and rotor, handlebar and both brake levers, switches and throttle, headlight and running lights, (empty) battery bag and mounting brackets... I weighted it all together when I took it off to replace the headset: 15 lbs 7 oz.
OK, all this is expansive, but not the best weight that can be achieved, only close to.

Now weight your pit bike front end and tell me. Or, if you want to compare fork only, mine is 6 lbs 4 oz with crowns and axle. Then you can consider that mine has all settings and tuning options: Sag, preload, low speed compression, high speed compression, rebound control with high/low hit gate, plus 5 pre-settable Mission Control levels.

I am not saying there is no good reason to fit a pit bike fork to an ebike, but sure not performance and safety.

PS. So far, my commuter ebike stopped shorter from 50 mph on dry pavement than any motorcycle, including those equipped with ABS.
Make it fool-proof, and I will make a better fool.
Current bikes
Street: https://s20.postimg.org/ewrvugywt/Session_04_2015.jpg
Dirt: https://s20.postimg.org/lbqwr55ml/IMG_0157.jpg

markz   100 GW

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Re: dirt bike fork on ebike

Post by markz » May 05 2019 9:52pm



redsite001
6 years ago
HECK YEAH IT'S HEAVY! Lol the fork is off of a 1985 honda cr500 frame. I have jumped it and it suprisingly stays level in the air, just a bit hard to wheelie! Thanks.
redsite001
7 years ago
@96motorhead the fork felt nice, but the back never was plush and had no rebound control at all. But it could handle drops really well and almost never bottomed out. the front was nice but the rear wasn't very good. It had 14'' travel in the back and 10 1/2'' up front
redsite001
1 month ago
It's been years and years. Both of those bikes are broken now sadly. The big one never was practical but it did have ridiculous travel


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